Abstract 3236: Discovery of hydrazide-based HDAC8 selective PROTACs

Abstract HDAC8 plays crucial roles in biological processes and is a highly desirable target for therapeutic interventions. However, due to the conserved catalytic domain among HDACs, developing specific inhibitors for these isozymes has proven challenging. HDAC8 also has deacetylase-independent activity which cannot be blocked by an inhibitor. Previously we reported the discoveries of a potent HDAC3 degrader XZ9002 and an HDAC3/8 dual degrader YX968. In this study, we carried out further optimizations based on the warhead of YX968 through rational design, which led to the discovery of YX862 and YL246, novel hydrazide-based HDAC8 selective PROTAC degraders with single-digit nanomolar DC50 and excellent selectivity. We demonstrated that the degradation of HDAC8 affects its non-histone substrates; however, it does not trigger profound histone hyper-acetylation and gene expression alteration, highlighting the unique role of HDAC8. The PROTACs developed in this study are well-characterized HDAC8 degraders without triggering pan-HDAC inhibition which represent valuable tool compounds for exploring the biological and therapeutic potential of HDAC8 in cancers and beyond. Citation Format: Yufeng Xiao, Yi Liu, Nikee Awasthee, Chengcheng Meng, Michael He, Seth Hale, Rashmi Karki, Zongtao Lin, Robert Kridel, Daiqing Liao, Guangrong Zheng. Discovery of hydrazide-based HDAC8 selective PROTACs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3236.